3GPP (3rd Generation Partnership Project), a standard specification for mobile communication systems, introduces dual connectivity as a technique for a communication terminal UE (User Equipment) to carry out wideband and low-delay communications. The dual connectivity is a technique that allows a UE to have dual connections to a first base station MeNB (Master evolved NodeB) and a second base station SeNB (Secondary eNB) that perform LTE (Long Term Evolution) communications, for example, so that the UE communicates not only with the MeNB but also with the SeNB. This improves the throughput of communications.
Non Patent Literature 1 describes, as a dual connectivity procedure, a process flow or the like where a UE newly adds an SeNB as an eNB to communicate with the UE when the UE is being connected with an MeNB.
On the other hand, areas where wireless LAN (Local Area Network) communications, which enable high-speed communications although the coverage area is smaller than mobile communication systems, are available have been expanded recently. Thus, a technique where a UE connects to both an eNB that performs mobile communications and an access point WT (Wireless LAN Termination) that performs wireless LAN communications by applying the dual connectivity technology, and the UE communicates not only with the eNB but also with the WT (which is referred to hereinafter as LTE-WT aggregation, which may also be referred to as LTE-WT dual connectivity), has also been studied. To be more specific, the background, object and the like of this study are described in Non Patent Literature 2.
Note that a charging rate to be applied to a UE is determined on the basis of a radio access technology (RAT) being used by the UE. For example, when a UE is performing LTE communications with an MeNB and an SeNB in dual connectivity, a charging rate determined at the time of LTE communications is applied to the UE. Non Patent Literature 3 describes a PCC (Policy and Charging Control) architecture for carrying out policy control and charging control.
Non Patent Literature 4 describes that a gateway device PGW (Packet Date Network Gateway) manages RAT types on a UE-by-UE basis as parameters related to charging. The RAT type is a parameter indicating a RAT that is currently used by a UE.